This invention relates to an apparatus for automatically filling and sealing thermoplastic bags using heat sealing means. In particular, it relates to an apparatus for filling and sealing large bulk thermoplastic bags which when filled can weigh several hundred kilograms.
Many examples of bag sealers which employ heat are known. U.S. Pat. No. 4,378,266, for example, discloses a relatively small manual device for use in the home which comprises stationary and compression elements pivotally connected. The stationary element provides a heated surface which fuses the open ends of a plastic bag when the compression element is rotated against the stationary element. This device seals adequately but is unsuitable for larger industrial applications where large bulk bags are involved. Further, it does not provide automatic bag filling means.
Several patents are directed to bag sealers for use in an industrial environment. In U.S. Pat. No. 4,574,560, grippers are used to hold the end of a sack in a vertical position and stretch it along its width. Pressure bars hold the sack end below the grippers while heated welding and backing bars seal the sack end after adhesive has been discharged onto the sack end. This device also seals satisfactorily but it too does not incorporate automatic bag filling means and the use of adhesive unnecessarily complicates the device.
U.S. Pat. No. 4,071,999 discloses a bag sealer employing heat sealing means. In this device, a carriage inserts hydraulically controlled hook-shaped fingers which pull the mouth of a filled bag taut while opposing pusher fingers push inwardly to form folds. A heat sealer comprising a two part clamp than clamps the opening of the taut bag and seals the contents therein. Once again a heat sealer is described which has no adequate bag filling means.
In short, while all of the patents discussed above function adequately as bag sealers, none of them include automatic bag filling means which cooperate with the bag sealing equipment.